Loop imaging catheter

ABSTRACT

An ultrasonic imaging catheter is used to generate a three-dimensional image of an organ having a relatively large cavity, such as, e.g., a heart. The catheter includes an elongate catheter body having an acoustic window formed at its distal end. The catheter further includes an imaging core, which includes a drive cable with a distally mounted ultrasonic transducer. The transducer is disposed in the acoustic window and is rotationally and longitudinally translatable relative thereto, providing the catheter with longitudinal scanning capability. The catheter further includes a pull wire, which is connected to the distal end of the catheter body, such that longitudinal displacement of the pull wire causes the acoustic window to bend into a known and repeatable arc. The catheter can then be operated to generate a longitudinal scan of the organ through the arc, i.e., a multitude of cross-sectional imaging data slices are generated along a continuously varying multitude of imaging planes, which intersect all regions of the body organ. In this manner, a three-dimensional image depicting the entire body organ can be generated from a single longitudinal scan.

FIELD OF THE INVENTION

The present invention pertains to medical imaging devices, and moreparticularly, to ultrasonic imaging catheters used in diagnosticapplications.

BACKGROUND

Presently, minimally invasive imaging devices are employed in thediagnostic analysis of relatively large body cavities, such as, e.g., aheart chamber. Of particular interest to the present invention,ultrasonic imaging catheters have been employed to generatecross-sectional images from within the body cavity. The cross-sectionalimages reveal the surrounding contour of tissue, secondary structure,and other structural information relevant to treatment and diagnosis ofvarious diseased conditions.

In this connection, a known imaging catheter 20, as depicted in FIG. 1,includes an elongate catheter body 22 with a distally formed elongateacoustic window 24 through which ultrasonic energy transparently passes.The catheter body 22 includes an imaging lumen 26 in which a rotatablyand longitudinally translatable imaging core 28 is disposed. The imagingcore 28 comprises a drive cable 30 along with a distally connectedultrasonic transducer housing 32 and mounted ultrasonic transducer 34.The transducer 34 is mechanically coupled to a drive unit (not shown)via the drive cable 30 and electrically coupled to a signal processor(not shown) via a transmission line 36 disposed in the drive cable 30.The transmission line 36 may consist of coaxial cable, triaxial cable,twisted pair, or other suitable configurations.

Disposal of the acoustic window 24, at a desired region within the bodycavity and subsequent operation of the drive unit and signal processor,generates a longitudinal image scan of the tissue surrounding the bodycavity. In particular, the electrical signals are transmitted to andreceived from the transducer 34, while the transducer 34 is rotationallyand longitudinally translated relative to the acoustic window 24. Inthis manner, a multitude of imaging data "slices" are generated, whichcan be synthesized to produce a three-dimensional image of the bodycavity for analysis by a viewing physician.

The ability to generate a three-dimensional image of a body cavity isadvantageous in several respects. First, such an image generally allowsa physician to ascertain the existence of a diseased region within thebody cavity. Second, if such diseased region is found, the image permitsa qualitative assessment of the nature of the disease in order to helpselect the most effective treatment modality. Third, the image can beused to determine the exact location of the diseased region, or thelocation of a therapeutic element relative to the diseased region, sothat intervention can be directed only at the diseased region and not athealthy regions of the body cavity where the interventional proceduremight cause damage.

Referring to FIG. 2, the imaging catheter 20 can be used to generate athree-dimensional image of a region of a heart 50. In particular, theimaging catheter 20 is advanced through the vasculature of the patientuntil the acoustic window 24 extends into a chamber of the heart 50,such as, e.g., the left ventricle 52. A longitudinal scan of the heart50 is then performed, thereby generating a multitude of cross-sectionalimaging data slices along respective imaging planes, such as, e.g.,representative planes P(1)-P(5). Subsequent synthesis of the imagingdata slices will result in a single three-dimensional image of hearttissue 50 which is intersected by the imaging planes. Heart tissue 50not intersected by the imaging planes, such as, e.g., at the apex 54 ofthe heart 50, will not appear in the three-dimensional image. Thus, theimage will not include potentially vital information that could lead tothe proper diagnosis and subsequent treatment of a diseased region ofthe heart 50.

As shown in FIG. 3, the acoustic window 38 can be manipulated inside theheart 50, such that imaging planes of a subsequent longitudinal scan,such as, e.g., representative imaging planes P(6)-P(8), intersect hearttissue 50 not imaged during the first longitudinal scan, such as, e.g.,at the apex 54. This task may sometimes be difficult or tedious toperform, and even if apparently successful, may result in a multitude ofuncorrelated three-dimensional images, making proper examination of theheart 50 more difficult.

Further, referring back to FIG. 2, the force that the mitral valve 56and entrance 58 to the left atrium 60 of the heart 50 exerts on theacoustic window 24 may create an arc 38 in the acoustic window 24through which the heart 50 is imaged. As a result, the imaging dataslices which are generated along the imaging planes, such as, e.g.,planes P(4) and (P5), may, when synthesized, result in a image which isdistorted at the left atrium 60 and right atrium 62, since the relativerotational orientation of the imaging planes P(4) and P(5) are unknowndue to the randomness of the geometry of the arc 38.

SUMMARY OF THE INVENTION

The present invention overcomes the afore-described drawbacks of aconventional imaging device by providing an imaging device, such as,e.g., an ultrasonic imaging catheter, that includes a pull wireconnected to the distal end thereof, such that manipulation of the pullwire forms the distal end of the imaging device into a curvilineargeometry that is known and repeatable.

In a first preferred embodiment, an ultrasonic imaging catheter,according to the present invention, includes an elongate catheter bodywith a distally formed acoustic window. An imaging core, which includesa drive cable and a distally mounted ultrasonic transducer, is disposedin an imaging lumen of the catheter body. The transducer is disposed inthe acoustic window and is rotationally and longitudinally translatablerelative thereto. The pull wire is disposed within a pull wire lumen,which may be the same as the imaging lumen, of the catheter body and isconnected to the distal tip of the acoustic window. Longitudinaldisplacement of the pull wire, relative to the catheter body, causes theacoustic window to form into a known and repeatable arc. A stiffeningmember can be disposed along the acoustic window to provide resiliencethereto.

In a preferred imaging method, the acoustic window of the catheter isplaced within a cavity of an organ, such as, e.g., the left ventricle ofa heart. The acoustic window is formed into an arc, and a curvilinearlongitudinal imaging scan is performed through the arc, generating amultitude of cross-sectional imaging data slices respectively along amultitude of imaging planes. Due to the curvature of the acousticwindow, the imaging planes have differing relative rotationalorientations, which intersect the entire body cavity, thereby providinga single three-dimensional image of virtually the entire body cavity.Since the geometry of the arc is known, any distortion caused by thecurvature of the acoustic window can be removed from thethree-dimensional image.

In an alternatively preferred imaging method, the imaging catheter isused in conjunction with a therapeutic catheter having a distallylocated therapeutic element, such as, e.g., an ablation electrode. Theacoustic window of the imaging catheter and the ablation electrode ofthe therapeutic catheter are placed in a body cavity, such as, e.g., theleft ventricle of a heart. The imaging catheter is operated, in asimilar manner as described above, to obtain a three-dimensional imageof the left ventricle. The image generally will include an acousticartifact caused by the ablation electrode, which can be used to locatethe ablation electrode adjacent the diseased region of the leftventricle for subsequent ablation thereof.

In still another alternatively preferred imaging method, the imagingcatheter is used in conjunction with another diagnostic catheter and atherapeutic catheter. The diagnostic catheter preferably includes adistal basket structure that includes an array of electrodes. Thetherapeutic catheter preferably includes a distal therapeutic element,such as, e.g., an ablation electrode. The acoustic window of the imagingcatheter, the basket structure of the diagnostic catheter, and theablation electrode of the therapeutic catheter are maneuvered into abody cavity, such as, e.g., the left ventricle of a heart. Thediagnostic catheter is operated to locate the diseased region of theventricle, with one of the diagnostic electrodes indicating the locationthereof. The imaging catheter is operated in a similar manner, asdescribed above, to obtain a three-dimensional image of body organ. Theimage may include a plurality of acoustic artifacts caused by thediagnostic electrodes and a single acoustic artifact caused by theablation electrode, which can both be used to locate the ablationelectrode adjacent the indicative diagnostic electrode, and thus, thediseased region, for subsequent ablation thereof.

Other and further objects, features, aspects, and advantages of thepresent invention will become better understood with the followingdetailed description of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate both the design and utility of preferredembodiments of the present invention, in which:

FIG. 1 is a partially cut-away side view of a prior art ultrasonicimaging catheter configured for generating a longitudinal imaging scanof a body cavity;

FIG. 2 is a plan view of the prior art catheter of FIG. 1 disposedwithin the left ventricle of a heart, particularly showing operation ofthe catheter to generate a multitude of cross-sectional imaging dataslices of the heart;

FIG. 3 is a plan view of the prior art catheter of FIG. 1 disposedwithin the left atrium of a heart, particularly showing operation of thecatheter to generate a multitude of cross-sectional imaging data slicesof the heart;

FIG. 4A is a partially cut-away side view of the distal end of apreferred embodiment of an ultrasonic imaging catheter, wherein theacoustic window is configured to be formed into a known and repeatablecurvilinear geometry;

FIG. 4B is a partially cut-away side view of the proximal end of thecatheter of FIG. 4A;

FIG. 5 is a side view of the catheter of FIGS. 4A and 4B, particularlyshowing the acoustic window in a rectilinear geometry;

FIG. 6 is a side view of the catheter of FIGS. 4A and 4B, particularlyshowing the acoustic window in a curvilinear geometry;

FIGS. 7A-7E are partially cut-away side views of the curvilinearacoustic window of FIG. 6, particularly showing various imaging planesalong which cross-sectional imaging data slices can be generated;

FIG. 8 is a plan view of the catheter of FIGS. 4A and 4B disposed withinthe left ventricle of a heart, particularly showing operation of thecatheter to generate a multitude of cross-sectional imaging data slicesof the heart through the curvilinear acoustic window; and

FIG. 9 is a plan view of the catheter of FIGS. 4A and 4B, a diagnosticcatheter and a therapeutic catheter disposed within the left ventricleof a heart, wherein the diagnostic catheter is operated to locate adiseased region, and the imaging catheter is operated to locate anablation electrode of the therapeutic catheter adjacent the diseasedregion.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 4A and 4B, a first exemplary loop imaging catheter100, according to the present invention, is configured to provide athree-dimensional image of an organ with a relatively large cavity, suchas, e.g., the heart 50 (FIGS. 2 and 3), when used in connection with adrive unit, signal processing circuitry and monitor (all not shown). Thecatheter 100 generally includes an elongate catheter body 102 with aproximal catheter end 104 (FIG. 4B) and a distal catheter end 106 (FIG.4A), which forms a distal acoustic window 108 with a distal tip 110; arotatably and longitudinally movable ultrasonic transducer 112 disposedin the acoustic window 108; a pull wire 114 connected to the distal tip110 of the acoustic window 108; and a stiffening member 116 disposed inthe acoustic window 108.

In particular, the catheter body 102 is composed of a biologicallycompatible material that provides both structural integrity to theimaging catheter 100, as well as a smooth outer surface for ease inaxial movement through a patient's body passage (e.g., the vascularsystem) with minimal friction. Such materials are typically made fromnatural or synthetic polymers, such as, e.g., silicone, rubber, naturalrubber, polyethylene, polyvinylchloride, polyurethanes, polyesters,polytetrafluoroethylenes (PTFE) and the like. The catheter body 102 maybe formed as a composite having a reinforcement material incorporatedwithin the polymeric body in order to enhance its strength, flexibility,and durability. Suitable enforcement layers include wire mesh layers,and the like. The flexible tubular elements of the catheter body 102will normally be formed by extrusion. If desired, the catheter diametercan be modified by heat expansion and shrinkage using conventionaltechniques.

The acoustic window 108 is made of material that is substantiallytransparent to ultrasonic energy, such as, e.g., a low densitypolyethylene. The acoustic window 108 has an elongated length tofacilitate longitudinal movement of the transducer 112 therein. Itshould be noted that the acoustic window 108 includes any structure thatallows ultrasonic energy to be transmitted between the transducer 112and body tissue.

The transducer 112 is mounted to a transducer housing 118, which isrotatably coupled to the drive unit via a flexible drive cable 120 toform an imaging core 122. The imaging core 122 is rotatably disposedwithin an imaging lumen 124, which extends substantially through thecatheter body 102 from the acoustic window 108 to the proximal catheterend 104.

The drive cable 120 is preferably designed such that it possesses a hightorsional stiffness and a low bending stiffness. For example, the drivecable 120 can be made of two counterwound layers of multifilar coilsthat are fabricated using techniques disclosed in Crowley et al., U.S.Pat. No. 4,951,677, which is fully incorporated herein by reference. Thedrive cable 120 is further reinforced to maintain its structuralintegrity during longitudinal movements thereof within the catheter body102. The transducer 112 is electrically coupled to the signal processorvia a transmission line 128, which are disposed in the drive cable 120.

Preferably, the drive unit is configured to automatically longitudinallytranslate the transducer 112, such as, e.g., the drive units describedin Webler et al., U.S. Pat. No. 5,592,942, issued Jan. 14, 1997, andcopending U.S. application Ser. No. 08/074,064, filed May 7, 1998, bothof which are expressly and fully incorporated herein by reference. Inthis manner, longitudinal movement of the transducer 112 within theacoustic window 108 is controlled in a uniform and consistent manner.

The pull wire 114 and stiffening member 116 are both disposed in a pullwire lumen 130, which extends the length of the catheter body 102. Thestiffening member 116 is composed of a suitable resilient material, suchas, e.g., Nitinol, to provide resilience to the acoustic window 108. Thestiffening member is preferably pre-shaped with a rectilinear geometry.The stiffening member 116 also acts as a conduit for the pull wire 114,allowing the pull wire 114 to be more easily longitudinally translatedrelative to the pull wire lumen 130. That is, the pull wire 114 issuitably attached to the distal tip 110 of the acoustic window 108 andextends through the center of the stiffening member 116 to the proximalcatheter end 104. The pull wire 114 preferably comprises a non-corrosivematerial such as, e.g., stainless steel, which can be coated with aTeflon material to reduce the friction between the pull wire 114 and thestiffening member 116. As will be described in further detail below, thestiffening member 116 urges the acoustic window 108 into a rectilineargeometry, i.e., the longitudinal axis 132 of the acoustic window 108 ismade rectilinear; while the pull wire 114 can be manipulated toconfigure the acoustic window 108 into a curvilinear geometry, i.e., thelongitudinal axis 132 of the acoustic window 108 is made curvilinear. Inalternative embodiments, the pull wire lumen 130 is the same as theimaging lumen 124.

The catheter 100 includes a catheter-drive unit interface 134, suitablymounted to the catheter body 102, to form the proximal catheter end 104thereof. The catheter-drive unit interface 134 provides the mechanicalinterface through which the drive unit exerts longitudinal and torsionalforces on the drive cable 120 to rotationally and longitudinallytranslate the transducer 112 relative to the acoustic window 108. Thecatheter-drive unit interface 134 also provides an electrical interface,typically via an inductive coupler (not shown), through which electricalsignals are conveyed between the rotating transducer 112 and thestationary drive unit/signal processor. The drive unit-catheterinterface 134 also includes an flush port 136, which is in fluidcommunication with the imaging lumen 124, to allow conveyance ofultrasonically transparent fluid therein. The drive unit-catheterinterface 134 also includes a pull wire entry port 138 from which thepull wire 114 extends, allowing manipulation of the pull wire 114 toalternately form the acoustic window 108 into rectilinear andcurvilinear geometries, as will be described in further detail below.

As depicted in FIG. 5, when the pull wire 114 is in a relaxed state(i.e., the pull wire 114 is not tightened), the acoustic window 108 isplaced into a substantially rectilinear geometry by the stiffeningmember 114. As depicted in FIG. 6, however, when the pull wire 114 is ina tensed state (i.e., the pull wire 114 is longitudinally displaced in aproximal direction relative to the acoustic window 108 as indicated bythe arrow 139), the acoustic window 108 is subjected to a compressiveforce, bending the acoustic window 108 into a substantially circular arc140 to form a curvilinear acoustic window 108'. The geometry of thecircular arc 140 is known and repeatable in that longitudinaldisplacement of the pull wire 114 by a certain distance L consistentlyresults in a circular arc 140 with a certain circumference C.

The circular arc 140 allows the catheter 100 to image body tissue alongvarious imaging planes. Referring to FIGS. 7A-7E, operation of the driveunit with the pull wire 114 longitudinally displaced a distance L,allows cross-sectional images to be generated along representativeimaging planes P(1)-P(5) when the transducer 112 is respectively locatedat corresponding points A(1)-A(5) along the circumference C of thecurvilinear acoustic window 108'. As will be described in further detailbelow, such a capability facilitates the generation of athree-dimensional image of substantially the entire body cavity via asingle longitudinal imaging scan.

The origin and relative rotational orientation of each imaging plane canbe determined from the corresponding longitudinal displacement M of thetransducer 112. For instance, if the transducer 112 is displaced adistance M(3), as depicted in FIG. 7C, it is known that the imagingplane P(3) has an origin at point A(3) along the circumference C of thecurvilinear acoustic window 108' and has a relative rotational positionof 0°. Similarly, if the transducer 112 is displaced a distance M(5), asdepicted in FIG. 7E, it is known that the imaging plane P(5) has anorigin at point A(5) along the circumference C of the curvilinearacoustic window 108' and has a relative rotational position of 90°. Aswill be described in further detail below, such a capability facilitatesthe generation of a three-dimensional image of a body cavity that is notdistorted.

With reference to FIG. 8, operation of the catheter 100 can now bedescribed in connection with the diagnosis of a body organ with arelatively large cavity, such as, e.g., the heart 50. The catheter body102 is introduced into a patient's body through an entrance point, suchas, e.g., the femoral artery, and routed through the vasculature via aguide wire and/or guide sheath (not shown) until the acoustic window 108is disposed within the left ventricle 52 of the heart 50. Ultrasonicallytransparent fluid, such as, e.g., saline solution, is conveyed into theimaging lumen 124 via the flush port 136 to fill the acoustic window 108(FIGS. 4A and 4B), enabling the transmission and reception of ultrasonicenergy through the fluid, through the acoustic window 108 and to andfrom the human anatomy. The pull wire 114 is then manipulated to formthe curvilinear acoustic window 108', i.e., the pull wire 114 islongitudinally displaced the distance L, such that the curvilinearacoustic window 108' forms the arc 140 with the known circumference C(FIG. 6).

The imaging core 122 is positioned within the catheter body 102, suchthat the transducer 112 is located at the most distal point A(1) on thecircumference C of the curvilinear acoustic window 108' (FIG. 7A). Thedrive unit is then operated to rotationally and longitudinally translatethe transducer 112 from point A(1) to point A(5) along the circumference(C) of the curvilinear acoustic window 108' (FIGS. 7A-7E), whiletransmitting and receiving electrical signals to the transducer 112. Inthis manner, a curvilinear longitudinal imaging scan of the heart 50 isperformed. That is, a multitude of raw cross-sectional imaging dataslices are generated respectively along a multitude of continuouslyvarying imaging planes, which perpendicularly intersect thecircumference C of the curvilinear acoustic window 108'. For purposes ofbrevity in illustration, FIG. 8 depicts only the five representativeimaging planes P(1)-P(5) at respective points A(1)-A(5) along thecircumference (C) of the curvilinear acoustic window 108'. In thismanner, the imaging planes intersect virtually the entire heart tissue50, and thus, the multitude of raw imaging data slices include all ofthe information necessary to perform a comprehensive analysis of theheart 50.

If synthesized, these raw imaging data slices would result in amultitude of cross-sectional images, which without alteration wouldresult in a three-dimensional image of the heart 50 that is distorteddue to the curvature of the curvilinear acoustic window 108'. The signalprocessor, however, removes any distortion in the three-dimensionalimage that would result from the raw cross-sectional images based on theknown curvature of the curvilinear acoustic window 108'. That is, amultitude of processed cross-sectional imaging data slices aregenerated, each of which is based on a corresponding raw imaging dataslice, the known circumference C of the arc 140, and a correspondinglongitudinal displacement M of the transducer 112. For example, the rawimaging data slice along the imaging plane P(2) can be modified based onthe circumference C of the arc 140 and the longitudinal displacementM(2) of the transducer 112, resulting in a corresponding processedimaging data slice. As described with respect to FIGS. 7A-7E, thecircumference C of the arc 140 can be determined from the longitudinaldisplacement L of the pull wire 114; and the origin and rotationalorientation of each of the imaging planes P can be determined from thecorresponding longitudinal displacements M of the transducer 112.

Alternatively, the circumference C of the curvilinear acoustic window108' can be determined based on the particular imaging plane that iscoextensive with the diameter D of the curvilinear acoustic window 108'(FIG. 6), and in this case imaging planes P(1) or P(5). In particular,if an imaging data slice is generated along one of these imaging planes,it will include an acoustic artifact caused by the pull wire 114,thereby allowing determination of the diameter D, and thus thecircumference C of the curvilinear acoustic window 108'. For instance,if the imaging data slice is generated along imaging plane P(1), theimaging data slice will include an acoustic artifact at point P(5),thereby allowing the distance between P(1) and P(5), i.e., the diameterD, to be calculated.

The multitude of processed imaging data slices are then synthesized,generating a single undistorted three-dimensional image of substantiallythe entire heart 50, which appears on the monitor for analysis by aviewing physician. The heart 50 can then be properly analyzed todetermine the existence and extent of any diseased tissue within theheart 50. The pull wire 114 can then be relaxed, so that the stiffeningmember 116 urges the curvilinear acoustic window 108 back into itsrectilinear geometry, allowing the catheter 100 to be extracted from thevasculature of the patient.

The adverse effects that cardiac motion may have on the accuracy of thethree-dimensional image may be minimized by gating the acquisition ofthe raw imaging data slices to coincide with the resting period (periodof minimal movement of heart tissue) of the cardiac cycle.

The loop imaging catheter 100 can be employed with other diagnosticand/or therapeutic equipment to more effectively diagnose and treatdiseased regions within a body cavity. For instance, as depicted in FIG.9, the catheter 100 can be employed with a diagnostic catheter 150 andan ablation catheter 160 to diagnose and treat infarcted tissue 158within the left ventricle 52 of the heart 50.

The diagnostic catheter 150 is configured to locate infarcted tissue 158(i.e., an area of dead tissue caused by insufficient blood supply)within the heart 50 and includes a distally located basket structure152, which carries an array of electrodes 154 on a multitude ofresilient splines 156. Localization of the infarcted tissue 158 isaccomplished by transmitting electrical signals between selected pairsof electrodes 154 (bipolar mode) or between selected electrodes 154 andan indifferent electrode (unipolar mode), and subsequently analyzing thereceived electrical signals. The ablation catheter 160 includes anablation electrode 162, which is configured to thermally destroymyocardial tissue, either by heating or cooling the tissue. Furtherdetails concerning the structure and method of using the diagnosticcatheter 150 and ablation catheter 160 are disclosed in Panescu et al.,U.S. Pat. No. 5,577,509, issued Nov. 26, 1996, which is fully andexpressly incorporated herein by reference.

In operation, the basket structure 152 of the diagnostic catheter 150,the ablation electrode 162 of the ablation catheter 160, and theacoustic window 108 of the imaging catheter 100 are configured withinthe left ventricle 52. The diagnostic basket structure 152 is configuredinto firm contact with the myocardial tissue of the left ventricle 52and operated to locate any infarcted tissue 158 within the leftventricle 52. The location of the infarcted tissue 158 can be expressedin terms of a specific electrode 154' within the array of electrodes154.

Once the infarcted tissue 158 is located, the acoustic window 108 of theimaging catheter 100 is formed into the curvilinear acoustic window108', and a curvilinear longitudinal imaging scan is performed togenerate a three-dimensional image of the left ventricle 52, in asimilar manner as that described above with respect to FIG. 8. Withinthe image, there will appear an array of acoustic artifacts caused bythe array of diagnostic electrodes 154 and a single acoustic artifactcaused by the ablation electrode 162. One of the array of acousticartifacts represents the indicative electrode 154', thereby providingknowledge of the location of the ablation electrode 162 relative to theindicative electrode 154'. The ablation electrode 162 can then beprecisely placed into firm contact with the infarcted tissue 158 forsubsequent ablation thereof. Prior to ablation, the imaging catheter 100can again be operated to ensure that the ablation electrode 162 is infact in firm contact with the infarcted tissue 158.

The loop imaging catheter 100 can be employed with therapeuticequipment, with the imaging catheter 100 being used as the solediagnostic device. For instance, the loop imaging catheter 100 andablation catheter 160 can be disposed in the cavity of a body organ,such as, e.g., the ventricle 52 of the heart 50. The imaging catheter100 can be operated to perform a curvilinear longitudinal imaging scan,generating a three-dimensional image of the left ventricle 52. In theimage there may appear a diseased region 158 and an acoustic artifactcaused by the ablation electrode 162. With knowledge of the location ofthe ablation electrode 162 relative to the location of the diseasedregion 158 obtained from the acoustic artifact, the ablation electrode162 can be precisely placed into firm contact with the diseased region158 for subsequent ablation thereof.

While preferred embodiments have been shown and described, it will beapparent to one of ordinary skill in the art that numerous alterationsmay be made without departing from the spirit or scope of the invention.Therefore, the invention is not to be limited except in accordance withthe following claims.

What is claimed:
 1. An imaging device, comprising:an elongate tubularbody including a distal elongate acoustic window, the tubular bodyforming an imaging lumen and a pull wire lumen; an imaging core disposedin the imaging lumen, the imaging core including a drive cable and adistally disposed ultrasonic transducer, the transducer being disposedin the acoustic window and rotatably and longitudinally movable relativeto the acoustic window; and a pull wire disposed in the pull wire lumen,the pull wire being mechanically coupled to the acoustic window.
 2. Theimaging device of claim 1, wherein the imaging lumen and pull wire lumenare distinct.
 3. The imaging device of claim 1, wherein the elongatetubular body is a catheter body.
 4. The imaging device of claim 1,further comprising a stiffening member disposed along the acousticwindow.
 5. The imaging device of claim 4, wherein the stiffening memberis configured to urge the acoustic window into a rectilinear geometry,and wherein the pull wire is configured to allow manipulation of theacoustic window into a curvilinear geometry.
 6. The imaging device ofclaim 5, wherein the acoustic window is configured to form a knownsubstantially circular arc when the pull wire is displaced a certainlongitudinal distance.
 7. The imaging device of claim 4, wherein thestiffening member is a tube disposed in the pull wire lumen, and whereinthe pull wire is disposed in the stiffening member.
 8. The imagingdevice of claim 1, wherein the pull wire is connected to a distal tip ofthe acoustic window.
 9. A method of imaging a body cavity using animaging device, the imaging device including a distal end and configuredfor performing a longitudinal scan of the body cavity, the methodcomprising:advancing the distal end of the imaging device into the bodycavity; bending the distal end of the imaging device into apredetermined arc; and performing a longitudinal scan of the body cavitythrough the arc to generate a plurality of imaging data slicesrespectively along a plurality of imaging planes, the plurality ofimaging planes having differing relative rotational orientations. 10.The method of claim 9, wherein the imaging device further includes apull wire mechanically coupled to a distal tip of the imaging device,and wherein the pull wire is longitudinally displaced to bend the distalend of the imaging device into the arc.
 11. The method of claim 9,further comprising determining the circumference of the arc.
 12. Themethod of claim 11, wherein the circumference of the arc is selectivelydeterminable based on the longitudinal displacement of the pull wire.13. The method of claim 11, wherein the longitudinal scan is performedthrough the pull wire to generate an acoustic artifact in at least oneof the imaging data slices, and the circumference of the arc isdetermined based on the acoustic artifact.
 14. The method of claim 11,wherein the plurality of imaging data slices are distorted, and whereinthe method further comprises generating a plurality of processed imagingdata slices, each of which is derived from a corresponding imaging dataslice, the circumference of the arc, and a corresponding longitudinaldisplacement of the ultrasonic transducer.
 15. The method of claim 14,further comprising generating a three-dimensional image of the bodycavity based on the plurality of processed imaging data slices.
 16. Themethod of claim 9, wherein the body cavity is a heart chamber.
 17. Themethod of claim 9, wherein the imaging device is an ultrasonic imagingcatheter.
 18. A method of imaging a body cavity using an imagingcatheter and a therapeutic catheter, the imaging catheter including adistal end and configured for performing a longitudinal scan of the bodycavity, the therapeutic catheter including a therapeutic element andconfigured for treating diseased tissue, the method comprising:advancingthe distal end of the imaging catheter into the body cavity; advancingthe therapeutic element of the therapeutic catheter into the bodycavity; bending the distal end of the imaging device into apredetermined arc with a known circumference; performing a curvilinearlongitudinal scan of the body cavity through the arc to generate aplurality of imaging data slices respectively along a plurality ofimaging planes with differing relative rotational orientations;generating a three-dimensional image of the body cavity based on theplurality of imaging data slices, and determining the location of adiseased region in the body cavity based on the image; and treating thediseased region with the ablation electrode.
 19. The method of claim18,wherein at least one of the plurality of imaging data slices includesan acoustic artifact caused by the therapeutic element; and furthercomprising locating the therapeutic element adjacent the diseased regionbased on the acoustic artifact.
 20. The method of claim 18, furtherusing a diagnostic catheter with a distal basket structure, thediagnostic catheter configured for locating diseased tissue, the methodfurther comprising:advancing the basket structure of the diagnosticcatheter into the body cavity; and diagnosing the body cavity with thediagnostic catheter to locate the diseased tissue.
 21. The method ofclaim 20,wherein the basket structure includes an array of diagnosticelectrodes; wherein at least one of the imaging data slices includes anacoustic artifact caused by a diagnostic electrode that is indicative ofthe diseased tissue location, and at least one of the imaging dataslices includes an acoustic artifact caused by the therapeutic element;and further comprising locating the therapeutic element adjacent thediseased region based on the acoustic artifacts.